Mediators of proliferation and differentiation for hematopoietic progenitor cells of all lineages are frequently present in the same conditioned medium. Although these secreted growth factors have similar molecular mass [usually between 25 to 35 kilo Daltons ("Kd")] and may have apparently overlapping functional properties, they are products of distinct genes.
Hematopoietic growth factors include factors which stimulate development of certain hematopoietic cell lineages: IL-3, which has multi-lineage activity; GM-CSF, which predominantly stimulates granulocyte and macrophage colony formation, although, under certain conditions, it may stimulate megakaryocytic lineage cells as well; CSF-1, which stimulates only macrophage colonies; and G-CSF, which stimulates only granulocyte colony formation. None of these growth factors have a molecular mass ("IMW") exceeding about 30 Kd.
Hematopoietic growth factors may be used in treating immune-compromised patients, including Acquired Immunodeficiency Syndrome "AIDS" patients and certain types of cancer patients. Accordingly, it is desirable to obtain additional hematopoietic growth factors for existing and new applications.